Compiler/platform abstraction
lwIP » Porting (system abstraction layer)

## Macros

#define | BYTE_ORDER LITTLE_ENDIAN
#define | LWIP_RAND() ((u32_t)rand())
#define | LWIP_PLATFORM_DIAG(x) do {printf x;} while(0)
#define | LWIP_PLATFORM_ASSERT(x)
#define | LWIP_NO_STDDEF_H 0
#define | LWIP_NO_STDINT_H 0
#define | LWIP_NO_INTTYPES_H 0
#define | LWIP_NO_LIMITS_H 0
#define | LWIP_NO_CTYPE_H 0
#define | LWIP_CONST_CAST(target_type, val) ((target_type)((ptrdiff_t)val))
#define | LWIP_ALIGNMENT_CAST(target_type, val) LWIP_CONST_CAST(target_type, val)
#define | LWIP_PTR_NUMERIC_CAST(target_type, val) LWIP_CONST_CAST(target_type, val)
#define | LWIP_PACKED_CAST(target_type, val) LWIP_CONST_CAST(target_type, val)
#define | LWIP_DECLARE_MEMORY_ALIGNED(variable_name, size) u8_t variable_name[LWIP_MEM_ALIGN_BUFFER(size)]
#define | LWIP_MEM_ALIGN_SIZE(size) (((size) + MEM_ALIGNMENT - 1U) & ~(MEM_ALIGNMENT-1U))
#define | LWIP_MEM_ALIGN_BUFFER(size) (((size) + MEM_ALIGNMENT - 1U))
#define | LWIP_MEM_ALIGN(addr) ((void *)(((mem_ptr_t)(addr) + MEM_ALIGNMENT - 1) & ~(mem_ptr_t)(MEM_ALIGNMENT-1)))
#define | PACK_STRUCT_BEGIN
#define | PACK_STRUCT_END
#define | PACK_STRUCT_STRUCT
#define | PACK_STRUCT_FIELD(x) x
#define | PACK_STRUCT_FLD_8(x) PACK_STRUCT_FIELD(x)
#define | PACK_STRUCT_FLD_S(x) PACK_STRUCT_FIELD(x)
#define | PACK_STRUCT_USE_INCLUDES
#define | LWIP_UNUSED_ARG(x) (void)x
#define | LWIP_PROVIDE_ERRNO

## Detailed Description

All defines related to this section must not be placed in lwipopts.h, but in arch/cc.h! If the compiler does not provide memset() this file must include a definition of it, or include a file which defines it. These options cannot be #defined in lwipopts.h since they are not options of lwIP itself, but options of the lwIP port to your system.

## Macro Definition Documentation

## BYTE_ORDER

#define BYTE_ORDER LITTLE_ENDIAN

Define the byte order of the system. Needed for conversion of network data to host byte order. Allowed values: LITTLE_ENDIAN and BIG_ENDIAN

## LWIP_ALIGNMENT_CAST

#define LWIP_ALIGNMENT_CAST | ( |  | target_type,
|  |  | val
| ) |  | LWIP_CONST_CAST(target_type, val)

Get rid of alignment cast warnings (GCC -Wcast-align)

## LWIP_CONST_CAST

#define LWIP_CONST_CAST | ( |  | target_type,
|  |  | val
| ) |  | ((target_type)((ptrdiff_t)val))

C++ const_cast<target_type>(val) equivalent to remove constness from a value (GCC -Wcast-qual)

## LWIP_DECLARE_MEMORY_ALIGNED

#define LWIP_DECLARE_MEMORY_ALIGNED | ( |  | variable_name,
|  |  | size
| ) |  | u8_t variable_name[LWIP_MEM_ALIGN_BUFFER(size)]

Allocates a memory buffer of specified size that is of sufficient size to align its start address using LWIP_MEM_ALIGN. You can declare your own version here e.g. to enforce alignment without adding trailing padding bytes (see LWIP_MEM_ALIGN_BUFFER) or your own section placement requirements.
e.g. if you use gcc and need 32 bit alignment:
#define LWIP_DECLARE_MEMORY_ALIGNED(variable_name, size) u8_t variable_name[size] __attribute__((aligned(4)))
or more portable:
#define LWIP_DECLARE_MEMORY_ALIGNED(variable_name, size) u32_t variable_name[(size + sizeof(u32_t) - 1) / sizeof(u32_t)]

## LWIP_MEM_ALIGN

#define LWIP_MEM_ALIGN | ( |  | addr | ) | ((void *)(((mem_ptr_t)(addr) + MEM_ALIGNMENT - 1) & ~(mem_ptr_t)(MEM_ALIGNMENT-1)))

Align a memory pointer to the alignment defined by MEM_ALIGNMENT so that ADDR % MEM_ALIGNMENT == 0

## LWIP_MEM_ALIGN_BUFFER

#define LWIP_MEM_ALIGN_BUFFER | ( |  | size | ) | (((size) + MEM_ALIGNMENT - 1U))

Calculate safe memory size for an aligned buffer when using an unaligned type as storage. This includes a safety-margin on (MEM_ALIGNMENT - 1) at the start (e.g. if buffer is u8_t[] and actual data will be u32_t*)

## LWIP_MEM_ALIGN_SIZE

#define LWIP_MEM_ALIGN_SIZE | ( |  | size | ) | (((size) + MEM_ALIGNMENT - 1U) & ~(MEM_ALIGNMENT-1U))

Calculate memory size for an aligned buffer - returns the next highest multiple of MEM_ALIGNMENT (e.g. LWIP_MEM_ALIGN_SIZE(3) and LWIP_MEM_ALIGN_SIZE(4) will both yield 4 for MEM_ALIGNMENT == 4).

## LWIP_NO_CTYPE_H

#define LWIP_NO_CTYPE_H 0

Define this to 1 in arch/cc.h of your port if your compiler does not provide the ctype.h header. If ctype.h is available, a few character functions are mapped to the appropriate functions (lwip_islower, lwip_isdigit...), if not, a private implementation is provided.

## LWIP_NO_INTTYPES_H

#define LWIP_NO_INTTYPES_H 0

Define this to 1 in arch/cc.h of your port if your compiler does not provide the inttypes.h header. You need to define the format strings listed in lwip/arch.h yourself in this case (X8_F, U16_F...).

## LWIP_NO_LIMITS_H

#define LWIP_NO_LIMITS_H 0

Define this to 1 in arch/cc.h of your port if your compiler does not provide the limits.h header. You need to define the type limits yourself in this case (e.g. INT_MAX, SSIZE_MAX).

## LWIP_NO_STDDEF_H

#define LWIP_NO_STDDEF_H 0

Define this to 1 in arch/cc.h of your port if you do not want to include stddef.h header to get size_t. You need to typedef size_t by yourself in this case.

## LWIP_NO_STDINT_H

#define LWIP_NO_STDINT_H 0

Define this to 1 in arch/cc.h of your port if your compiler does not provide the stdint.h header. You need to typedef the generic types listed in lwip/arch.h yourself in this case (u8_t, u16_t...).

## LWIP_PACKED_CAST

#define LWIP_PACKED_CAST | ( |  | target_type,
|  |  | val
| ) |  | LWIP_CONST_CAST(target_type, val)

Avoid warnings/errors related to implicitly casting away packed attributes by doing a explicit cast

## LWIP_PLATFORM_ASSERT

#define LWIP_PLATFORM_ASSERT | ( |  | x | ) |

Value:
do {printf("Assertion \"%s\" failed at line %d in %s\n", \
x, __LINE__, __FILE__); fflush(NULL); abort();} while(0)

Platform specific assertion handling.
Note the default implementation pulls in printf, fflush and abort, which may in turn pull in a lot of standard library code. In resource-constrained systems, this should be defined to something less resource-consuming.

## LWIP_PLATFORM_DIAG

#define LWIP_PLATFORM_DIAG | ( |  | x | ) | do {printf x;} while(0)

Platform specific diagnostic output.
Note the default implementation pulls in printf, which may in turn pull in a lot of standard library code. In resource-constrained systems, this should be defined to something less resource-consuming.

## LWIP_PROVIDE_ERRNO

#define LWIP_PROVIDE_ERRNO

LWIP_PROVIDE_ERRNO==1: Let lwIP provide ERRNO values and the 'errno' variable. If this is disabled, cc.h must either define 'errno', include <errno.h>, define LWIP_ERRNO_STDINCLUDE to get <errno.h> included or define LWIP_ERRNO_INCLUDE to <errno.h> or equivalent.

## LWIP_PTR_NUMERIC_CAST

#define LWIP_PTR_NUMERIC_CAST | ( |  | target_type,
|  |  | val
| ) |  | LWIP_CONST_CAST(target_type, val)

Get rid of warnings related to pointer-to-numeric and vice-versa casts, e.g. "conversion from 'u8_t' to 'void *' of greater size"

## LWIP_RAND

#define LWIP_RAND | ( |  | ) | ((u32_t)rand())

Define random number generator function of your system

## LWIP_UNUSED_ARG

#define LWIP_UNUSED_ARG | ( |  | x | ) | (void)x

Eliminates compiler warning about unused arguments (GCC -Wextra -Wunused).

## PACK_STRUCT_BEGIN

#define PACK_STRUCT_BEGIN

Packed structs support. Placed BEFORE declaration of a packed struct.
For examples of packed struct declarations, see include/lwip/prot/ subfolder.
A port to GCC/clang is included in lwIP, if you use these compilers there is nothing to do here.

## PACK_STRUCT_END

#define PACK_STRUCT_END

Packed structs support. Placed AFTER declaration of a packed struct.
For examples of packed struct declarations, see include/lwip/prot/ subfolder.
A port to GCC/clang is included in lwIP, if you use these compilers there is nothing to do here.

## PACK_STRUCT_FIELD

#define PACK_STRUCT_FIELD | ( |  | x | ) | x

Packed structs support. Wraps u32_t and u16_t members.
For examples of packed struct declarations, see include/lwip/prot/ subfolder.
A port to GCC/clang is included in lwIP, if you use these compilers there is nothing to do here.

## PACK_STRUCT_FLD_8

#define PACK_STRUCT_FLD_8 | ( |  | x | ) | PACK_STRUCT_FIELD(x)

Packed structs support. Wraps u8_t members, where some compilers warn that packing is not necessary.
For examples of packed struct declarations, see include/lwip/prot/ subfolder.
A port to GCC/clang is included in lwIP, if you use these compilers there is nothing to do here.

## PACK_STRUCT_FLD_S

#define PACK_STRUCT_FLD_S | ( |  | x | ) | PACK_STRUCT_FIELD(x)

Packed structs support. Wraps members that are packed structs themselves, where some compilers warn that packing is not necessary.
For examples of packed struct declarations, see include/lwip/prot/ subfolder.
A port to GCC/clang is included in lwIP, if you use these compilers there is nothing to do here.

## PACK_STRUCT_STRUCT

#define PACK_STRUCT_STRUCT

Packed structs support. Placed between end of declaration of a packed struct and trailing semicolon.
For examples of packed struct declarations, see include/lwip/prot/ subfolder.
A port to GCC/clang is included in lwIP, if you use these compilers there is nothing to do here.

## PACK_STRUCT_USE_INCLUDES

#define PACK_STRUCT_USE_INCLUDES

PACK_STRUCT_USE_INCLUDES==1: Packed structs support using #include files before and after struct to be packed.
The file included BEFORE the struct is "arch/bpstruct.h".
The file included AFTER the struct is "arch/epstruct.h".
This can be used to implement struct packing on MS Visual C compilers, see the Win32 port in the lwIP/contrib subdir for reference. For examples of packed struct declarations, see include/lwip/prot/ subfolder.
A port to GCC/clang is included in lwIP, if you use these compilers there is nothing to do here.